1. Field of the Invention
The present invention relates to a method for producing a cathode active material for a non-aqueous electrolyte secondary battery, and more particularly, it relates to a method for producing a composite oxide containing nickel as a main component.
2. Description of the Prior Art
Recently, more and more audiovisual apparatus and electronic equipment such as a personal computer have been developed into portable and cordless type.
There is an increasing demand for a light and compact secondary battery having a high energy density as a power source for driving such equipment. Under such circumstances, a secondary battery using a non-aqueous electrolyte (hereinafter referred to as a non-aqueous electrolyte secondary battery), in particular, a lithium battery, is greatly expected to play a significant role as a battery providing a high voltage and a high energy density.
Examples of known cathode active materials for a non-aqueous electrolyte secondary battery include LiCoO.sub.2, LiNiO.sub.2, LiMnO.sub.2, and the like. A battery using LiCoO.sub.2 as a cathode material is already commercially available. LiNiO.sub.2 has, however, not been practically used because of its small discharge capacity.
Examples of a material for synthesizing LiNiO.sub.2 include Ni(OH).sub.2 and NiCO.sub.3 for a nickel salt and LiOH, LiNO.sub.3 and Li.sub.2 CO.sub.3 for a lithium salt. As Ni(OH).sub.2, a mixture of .alpha.-Ni(OH).sub.2 and .beta.-Ni(OH).sub.2 or .alpha.-Ni(OH).sub.2 alone has been used conventionally.
Carbon black has been used as an electrically conductive agent for a cathode, and a fluorocarbon polymer such as polytetrafluoroethylene and polyvinylidene fluoride as a binder.
Examples of a material for an anode include metal lithium, a lithium alloy and a carbon material which is intercalated or deintercalated with lithium.
A non-aqueous electrolyte secondary battery including conventionally prepared nickel composite oxide as a cathode active material, which is produced by heating a mixture of .alpha.-Ni(OH).sub.2 as a nickel salt and a lithium salt, poses a problem of a small discharge capacity.